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162173 Ryugu
162173 Ryugu.jpg
Monochrome view of Ryugu[a]
Discovery [1]
Discovered byLINEAR
Discovery siteLincoln Lab's ETS
Discovery date10 May 1999
MPC designation(162173) Ryugu
Named after
("Dragon palace")
1999 JU3
Apollo · NEO · PHA[1][2]
Orbital characteristics[2]
Epoch 12 December 2011 (JD 2455907.5)
Uncertainty parameter 0
Observation arc30.32 yr (11,075 d)
Aphelion1.4159 AU
Perihelion0.9633 AU
1.1896 AU
1.30 yr (474 d)
0° 45m 34.56s / day
Earth MOID0.0006 AU (0.2337 LD)
Physical characteristics
Mean diameter
0.865±0.015 km[3]
0.87 km[4]
0.90±0.14 km[5]
0.92±0.12 km[6]
0.980±0.029 km[7]
1.13±0.03 km[8]
Mass4.5×1011 kg[9]
Equatorial surface gravity
1/80,000 g[9]
7.627±0.007 h[7][10]
SMASS = Cg[2] · C[3]
18.69±0.07 (R)[4]

162173 Ryugu, provisional designation 1999 JU3, is a near-Earth object and a potentially hazardous asteroid of the Apollo group. It measures approximately 1 kilometer (0.6 mi) in diameter and is a dark object of the rare spectral type Cg, with qualities of both a C-type asteroid and a G-type asteroid. In June 2018, a spacecraft, Hayabusa2, arrived at the asteroid.[11]

YouTube Encyclopedic

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  • ✪ Why Japan Is Landing Hopping Robots On An Asteroid
  • ✪ Scientists Just Bombed A Giant Asteroid! *Ryugu*
  • ✪ Japanese Asteroid Rovers Touch Down - Hayabusa 2 Update
  • ✪ MINERVA-II1 rovers send images from asteroid Ryugu
  • ✪ How we landed a rover on an asteroid - BBC Click


- Narrator: On September 21, Japan's space agency made history. It became the first country to land not one, but two rovers onto an asteroid, and already, the two unmanned rovers have sent back the first images while on the surface. And no, so far, it's looking like there are no alien cities on its surface, but this mission, called Hayabusa2, could ultimately help solve one of the grandest scientific mysteries of all, where did life on Earth come from? (gentle orchestral music) Scientists have been studying asteroids for years. NASA, for example, landed its NEAR Shoemaker spacecraft on Asteroid Eros in 2001, but it's Japan's space agency that is the first to deploy a pair of rovers to explore an asteroid's surface. Japan launched the Hayabusa2 mission in December 2014, so, it has already been about 3 1/2 years in the making. The spacecraft rendezvoused with its target in June 2018, snapping a series of pictures that revealed the asteroid's shape. The asteroid of choice was 162173 Ryugu, or Ryugu for short. In Japanese, it refers to a magical, underwater dragon palace. Now, the asteroid flies through space around the sun every 16 months, conveniently, between the orbits of Earth and Mars, making it an ideal target for this mission, which, if all goes according to plan, it will return a sample of the asteroid to Earth by the early 2020s. As the spacecraft flew closer to the asteroid's surface, it prepared to deploy its first two unmanned rovers. But these guys aren't your typical space rover. They're slightly bigger than the size of a large iPhone, measuring just 7 by 18 centimeters, and they won't be driving around on the asteroid's surface. They'll be hopping. Yeah, you heard that right, hopping. Japan designed the rovers with a spinning cylinder inside that gives it the power to hop about a few meters at a time. This reduces the risk of getting stuck on the rocky, uneven surface, but it doesn't come without its own risks. Asteroids are relatively small and therefore, have a weak gravitational pull, and even by asteroid standards, Ryugu is tiny. It's less than a kilometer across, making it no larger than a few city blocks. So, if the rovers hop too high, they could potentially go flying off into space. But, so far, the mission looks good. The rovers have already achieved their first hop. Now, this may be the first time Japan has landed on an asteroid, but it won't be the last. These two rovers are just the first of four that Japan aims to land on Ryugu. The other two rovers are scheduled to land within the next year. In the process, Japan hopes to collect and return a sample of Ryugu to Earth, so that scientists can study it in more detail, looking for traces of water and organic material. If it turns out that asteroids like Ryugu contain similar material that we see on Earth, it would be strong evidence for the idea that life on Earth first came from asteroids billions of years ago. But this is a mystery that we can only answer if we study asteroids directly.



Discovery and name

Ryugu was discovered on 10 May 1999 by astronomers with the Lincoln Near-Earth Asteroid Research at the Lincoln Lab's ETS near Socorro, New Mexico, in the United States. It was given the provisional designation 1999 JU3.[1] The asteroid was officially named "Ryugu" by the Minor Planet Center on 28 September 2015 (M.P.C. 95804).[12] The name refers to Ryūgū (Dragon Palace), a magical underwater palace in a Japanese folktale. In the story, the fisherman Urashima Tarō travels to the palace on the back of a turtle, and when he returns, he carries with him a mysterious box, much like Hayabusa2 returning with samples.[1][13]


Orbit between Earth and Mars
Orbit between Earth and Mars


Ryugu orbits the Sun at a distance of 0.96–1.41 au once every 16 months (474 days; semi-major axis of 1.19 au). Its orbit has an eccentricity of 0.19 and an inclination of 6° with respect to the ecliptic.[2] It has a minimum orbital intersection distance with Earth of 95,400 km (0.000638 au), which translates into 0.23 lunar distance.[2]


Early analysis in 2012 by Thomas G. Müller et al. used data from a number of observatories, and suggested that the asteroid was "almost spherical", a fact that hinders precise conclusions, with retrograde rotation, an effective diameter of 0.85–0.88 kilometers, (0.528 miles) and a geometric albedo of 0.044 to 0.050. They estimated that the grain sizes of its surface materials are between 1 and 10 mm.[3]

Initial images taken by the Hayabusa2 spacecraft on approach at a distance of 700 km (434.9 miles) were released on 14 June 2018. They revealed a diamond shaped body and confirmed its retrograde rotation.[14] Between 17 and 18 June 2018, Hayabusa2 went from 330 km to 240 km (205.05 to 149.1 miles) from Ryugu and captured a series of additional images from the closer approach.[15] Astronomer Brian May created stereoscopic images from data collected a few days later.[16] After a few months of exploration, JAXA scientists concluded that Ryugu is actually a rubble pile with about 50% of its volume being empty space.[17]

The acceleration due to gravity at the equator has been evaluated at about 0.11 mm/s2 (0.00011 m/s2). It rises to 0.15 mm/s2 at the poles. The mass of Ryugu is estimated at about 450 million tons.[18]

Hayabusa2 mission

Animation of Hayabusa2's orbit from 3 December 2014 to 29 December 2019  Hayabusa2   162173 Ryugu   Earth   Sun
Animation of Hayabusa2's orbit from 3 December 2014 to 29 December 2019
  Hayabusa2   162173 Ryugu   Earth   Sun

The Japan Aerospace Exploration Agency (JAXA) spacecraft Hayabusa2 was launched in December 2014 and successfully arrived at the asteroid on 27 June 2018. It is planned to return material from the asteroid to Earth by December 2020.[19]

The Hayabusa2 mission includes four rovers with various scientific instruments. On 21 September 2018, the first two of these rovers, which hop around the surface of the asteroid, were released from Hayabusa2.[20] This marks the first time a mission has completed a successful landing on a fast-moving asteroid body.[21]

On 3 October 2018, the German-French Mobile Asteroid Surface Scout (MASCOT) lander successfully arrived on Ryugu, 10 days after the MINERVA rovers landed.[22] Its mission was short-lived, however, with only 16 hours available from its batteries.

Hayabusa2 touched down briefly February 22, 2019 on the Ryugu asteroid, fired a bullet into the surface to puff up dust for collection and blasted back to its holding position.[23]

The origin of 162173 Ryugu may be either 495 Eulalia or 142 Polana[24]   Sun ·    Earth ·    162173 Ryugu ·    142 Polana ·    495 Eulalia
The origin of 162173 Ryugu may be either 495 Eulalia or 142 Polana[24]
   Sun ·    Earth ·    162173 Ryugu ·    142 Polana ·    495 Eulalia

See also



  1. ^ Photograph of the full disc of 162173 Ryugu by the Optical Navigation Camera – Telescopic (ONC-T) instrument aboard the Hayabusa2 spacecraft. The photograph was taken on 26 June 2018, at a distance of 20 kilometres (12 miles) from the asteroid's surface.


  1. ^ a b c d e f "162173 Ryugu (1999 JU3)". Minor Planet Center. Retrieved 30 October 2018.
  2. ^ a b c d e f "JPL Small-Body Database Browser: 162173 Ryugu (1999 JU3)" (2016-08-09 last obs.). Jet Propulsion Laboratory. Retrieved 30 October 2018.
  3. ^ a b c d e Müller, T. G.; Durech, J.; Ishiguro, M.; Mueller, M.; Krühler, T.; Yang, H.; et al. (March 2017). "Hayabusa-2 mission target asteroid 162173 Ryugu (1999 JU3): Searching for the object's spin-axis orientation" (PDF). Astronomy and Astrophysics. 599: 25. arXiv:1611.05625. Bibcode:2017A&A...599A.103M. doi:10.1051/0004-6361/201629134. Retrieved 30 October 2018.
  4. ^ a b c Kim, Myung-Jin; Choi, Young-Jun; Moon, Hong-Kyu; Ishiguro, Masateru; Mottola, Stefano; Kaplan, Murat; et al. (February 2013). "Optical observations of NEA 162173 (1999 JU3) during the 2011-2012 apparition" (PDF). Astronomy and Astrophysics. 550: 4. arXiv:1302.4542. Bibcode:2013A&A...550L..11K. doi:10.1051/0004-6361/201220673. Retrieved 30 October 2018.
  5. ^ a b Campins, H.; Emery, J. P.; Kelley, M.; Fernández, Y.; Licandro, J.; Delbó, M.; et al. (August 2009). "Spitzer observations of spacecraft target 162173 (1999 JU3)" (PDF). Astronomy and Astrophysics. 503 (2): L17–L20. arXiv:0908.0796. Bibcode:2009A&A...503L..17C. doi:10.1051/0004-6361/200912374. Retrieved 30 October 2018.
  6. ^ a b c Hasegawa, S.; Müller, T. G.; Kawakami, K.; Kasuga, T.; Wada, T.; Ita, Y.; et al. (December 2008). "Albedo, Size, and Surface Characteristics of Hayabusa-2 Sample-Return Target 162173 1999 JU3 from AKARI and Subaru Observations". Publications of the Astronomical Society of Japan. 60 (SP2): S399––S405. Bibcode:2008PASJ...60S.399H. doi:10.1093/pasj/60.sp2.S399. Retrieved 30 October 2018.
  7. ^ a b c d Abe, M.; Kawakami, K.; Hasegawa, S.; Kuroda, D.; Yoshikawa, M.; Kasuga, T.; et al. (March 2008). "Ground-based Observational Campaign for Asteroid 162173 1999 JU3" (PDF). Lunar and Planetary Science: 1594. Bibcode:2008LPI....39.1594A. Retrieved 30 October 2018.
  8. ^ a b Yu, Liang-Liang; Ji, Jiang-Hui; Wang, Su (July 2014). "Investigation of Thermal Inertia and Surface Properties for Near-earth Asteroid (162173) 1999 JU3". Chinese Astronomy and Astrophysics. 38 (3): 317–329. Bibcode:2014ChA&A..38..317L. doi:10.1016/j.chinastron.2014.07.008. Retrieved 30 October 2018.
  9. ^ a b Clark, Stephen (6 September 2018). "Hayabusa 2 team sets dates for asteroid landings – Spaceflight Now". Retrieved 7 September 2018.
  10. ^ "LCDB Data for (162173) Ryugu". Asteroid Lightcurve Database (LCDB). Retrieved 30 October 2018.
  11. ^ Chang, Kenneth; Stirone, Shannon (19 March 2019). "The Asteroid Was Shooting Rocks Into Space. 'Were We Safe in Orbit?' - NASA's Osiris-Rex and Japan's Hayabusa2 spacecraft reached the space rocks they are surveying last year, and scientists from both teams announced early findings on Tuesday (03/19/2019)". The New York Times. Retrieved 21 March 2019.
  12. ^ "MPC/MPO/MPS Archive". Minor Planet Center. Retrieved 30 October 2018.
  13. ^ "Name Selection of Asteroid 1999 JU3 Target of the Asteroid Explorer "Hayabusa2"" (Press release). JAXA. 5 October 2015. Retrieved 30 October 2018.
  14. ^ "From a distance of about 700km, Ryugu's rotation was observed". JAXA. 16 June 2016. Retrieved 30 October 2018.
  15. ^ Plait, Phil (20 June 2018). "Asteroid Ryugu Starts to Come Into Focus". SyFy Wire. Retrieved 30 October 2018.
  16. ^ Bartels, Meghan (10 July 2018). "Queen's Brian May Will Rock You with This Stereo Image of Asteroid Ryugu". Retrieved 24 December 2018.
  17. ^ Hayabusa-2: Asteroid mission exploring a 'rubble pile'. Paul Rincon, BBC News. 19 March 2019.
  18. ^ Operation status for the asteroid explorer, Hayabusa2, in the vicinity of Ryugu (PDF), JAXA, 5 September 2018, retrieved 30 October 2018
  19. ^ "Current status of the asteroid explorer, Hayabusa2, leading up to arrival at asteroid Ryugu in 2018" (PDF). JAXA. 14 June 2016. Retrieved 30 October 2018.
  20. ^ Wall, Mike (21 September 2018). "Japanese Probe Deploys Tiny Hopping Robots Toward Big Asteroid Ryugu". Retrieved 30 October 2018.
  21. ^ Yoshimitsu, Tetsuo; Kubota, Takashi; Tsuda, Yuichi; Yoshikawa, Makoto (23 September 2015). "MINERVA-II1: Successful image capture, landing on Ryugu and hop!". JAXA Hayabusa2 Project. JAXA. Retrieved 30 October 2018.
  22. ^ "Touchdown! Japan space probe lands new robot on asteroid". 3 October 2018. Retrieved 30 October 2018.
  23. ^ Touchdown: Japan probe Hayabusa2 lands on distant asteroid. Kyoko Hasegawa, PhysOrg. February 22, 2019.
  24. ^ S. Sugita; et al. (19 Mar 2019). "The geomorphology, color, and thermal properties of Ryugu: Implications for parent-body processes". doi:10.1126/science.aaw0422.


External links

This page was last edited on 5 April 2019, at 21:11
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